Magnetic Resonance Imaging of an Experimental Model of Intracranial Metastatic Disease

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Abstract
RATIONALE AND OBJECTIVES. The detectability of brain metastases was evaluated in a rabbit model, with attention to magnetic resonance contrast dose and timing of image acquisition after injection of contrast medium. METHODS. Five New Zealand white rabbits were studied at 1.5 T 6 to 7 days and 11 to 12 days after surgical implantation of an adenocarcinoma tumor nidus. T l - and T2-wcighted spinecho images (0.9 X 0.9 X 2 mm3 voxel size) were obtained before administration of contrast medium. Tl-weighted images were repeated 5,15, and 30 minutes after intravenous injection of 0.1 mmol/kg gadoteridol. At 40 minutes, a supplemental dose of 0.2 mmol/kg (0.3 mmol/kg cumulative dose) was administered, with Tl-weighted images repeated at 5,15, and 30 minutes after the second injection. RESULTS. Six to 7 days after tumor implantation, lesion enhancement (percent change, with normalization to baseline and equilibrium values) was 42 ± 9% at 5 minutes, 48 ± 9% at 15 minutes, and 42 ± 10% at 30 minutes after administration of 0.1 mmol/kg gadoteridol. After administration of 0.3 mmol/kg gadoteridol, lesion enhancement was 111 ± 13% at 5 minutes, 116 ± 8% at 15 minutes, and 100% at 30 minutes. On film review, 2 of 5 lesions were not detectable at 6 to 7 days after tumor implantation with 0.1 mmol/kg gadoteridol. Administration of 0.3 mmol/kg gadoteridol provided for lesion identification in each instance. Eleven to 12 days after tumor implantation, one lesion was not detectable with 0.1 mmol/kg gadoteridol. Administration of 0.3 mmol/kg gadoteridol again provided for lesion identification in all cases. Mean lesion enhancement increased from 39 ± 15% to 104 ± 10%. CONCLUSIONS. The administration of 0.3 mmol/kg gadoteridol (high dose) compared with 0.1 mmol/kg gadoteridol (conventional dose) improves metastatic lesion detectability in the brain. The lesions identified only at high dose were confirmed by histopathology. Smaller lesions were not detected at a dose ofO.l mmol/kg.

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